Wind turbine collisions and the deadly bat disease known as white-nose syndrome (WNS) can together intensify the decline of endangered Indiana bat populations in the midwestern United States, according to a recently published U.S. Geological Survey study.

“Bats are valuable because, by eating insects, they save U.S. agriculture billions of dollars per year in pest control,” said USGS scientist Richard Erickson, the lead author of the study. “Our research is important for understanding the threats to endangered Indiana bats and can help inform conservation efforts.”

The researchers used a scientific model to compare how wind turbine mortality and WNS may singly and then together affect Indiana bat population dynamics throughout the species’ U.S. range. Findings from the model include:

Wind turbine deaths were localized and more likely to affect small sub-populations of bats, whereas WNS was more likely to devastate large winter colonies over the species’ entire range;

Together, the two threats reduced the sizes of all Indiana bat sub-populations;

WNS had the largest impact on population dynamics, with the most severe potential die-off scenario showing a population loss of about 95 percent; and

Despite killing fewer animals than WNS, wind turbines disrupted Indiana bat migration routes, which affected metapopulation dynamics more than WNS did in almost all modeled scenarios. A bat metapopulation consists of separated groups of the same species that interact during migration.

“These findings are useful for wildlife managers because they demonstrate the extra importance of protecting small Indiana bat colonies during the winter to help prevent extinction,” Erickson said.

WNS is not known to pose a threat to humans, pets, livestock or other wildlife.

This surveillance video from a temperature-imaging camera shows a bat interacting with a wind turbine at about 3 a.m. on a brightly moonlit summer night. (Paul Cryan, USGS)

Counties with known Indiana bat fatalities at wild facilities. The fatalities mapped are those known to the U.S. Fish and Wildlife Service as of April 2015. The figure is from “Indiana Bat Fatalities at Wind Energy Facilities” by Lori Pruitt and Jennifer Okajima, U.S. Fish and Wildlife Service, Indiana Field Office (http://www.fws.gov/midwest/wind/wildlifeimpacts/inbafatalities.html). (Public domain.)